WITHDRAWN: Effects of equivalence ratio and wall properties on the heat transfer characteristics of microchannel reactors for hydrogen production

Abstract

There is a continuing effort to perform steam reforming reactions in thermally integrated microchannel chemical reactors. However, the mechanisms for the effects of design factors on heat transfer characteristics are still not fully understood. This study relates to a thermochemical process for producing hydrogen by the catalytic endothermic reaction of methanol with steam in a thermally integrated microchannel reforming reactor. Computational fluid dynamics simulations are conducted to better understand the consumption, generation, and exchange of thermal energy between endothermic and exothermic processes in the reactor. The effects of equivalence ratio and wall properties on heat transfer characteristics and reactor performance are investigated. The results indicate that there are issues of efficiency loss for fuel-rich combustion cases. Loss of flame stability due to external heat losses are main issues that require thermal management. The thermal conductivity of the channel walls is fundamentally important. Materials with high thermal conductivity are preferred for the channel walls. Thermally conductive ceramics and metals are well-suited. Wall materials with poor heat conduction properties degrade the reactor performance. The heat released by the exothermic reaction could be entirely consumed by the endothermic reaction, thereby avoiding heat imbalances within the reactor or reducing the likelihood of the formation of hot spots within the catalyst layers. No flame combustion is involved in the process. Design recommendations are made to improve thermal performance for the reactor.